Drainage Search: What to Expect When Selling

When someone buys your property, their solicitor will order a drainage and water search as part of the standard property search pack. This search checks how your home connects to the public water supply and sewerage system, where the nearest public sewers and water mains run, and whether there are any issues that could affect the buyer's use of the property.

As a seller, the drainage search results will not come directly to you — they go to the buyer's solicitor. But the findings can trigger follow-up enquiries that you will need to answer. Understanding what the search covers, and what it might reveal about your property, helps you prepare and keep your sale moving.

What is a drainage and water search?

A drainage and water search is a formal enquiry submitted to the water and sewerage company responsible for the area where the property is located. In England and Wales, this is done using a standardised form called the CON29DW (Drainage and Water Enquiries), produced by the Law Society. The search is separate from the local authority search and the environmental search, both of which cover different types of information.

There are several regional water and sewerage companies in England and Wales, including Thames Water, Severn Trent Water, United Utilities, Yorkshire Water, Anglian Water, Southern Water, Welsh Water (Dwr Cymru), Wessex Water, Northumbrian Water, and South West Water. The search is submitted to whichever company serves the property's location.

The CON29DW form is divided into two parts. The standard enquiries cover the information most buyers and mortgage lenders require. Optional additional enquiries can be added for properties in unusual situations, such as those near sewage treatment works or in areas with combined sewer systems.

What the drainage search reveals

The CON29DW covers a range of questions about the property's water and drainage arrangements. Here is a summary of the key areas and what each one tells the buyer.

Public sewers, shared drains, and who is responsible

One of the most important things the drainage search reveals is how the property's drainage connects to the public sewer network — and who is responsible for maintaining each part of that system. This is an area that often confuses sellers and buyers alike, so it is worth understanding the terminology.

Private drains

A private drain serves a single property. It runs from the property to the point where it connects to a shared drain or a public sewer. The property owner is responsible for maintaining and repairing it. If a blockage occurs in your private drain, the cost of fixing it is yours.

Shared (lateral) drains

A shared drain, sometimes called a lateral drain, serves two or more properties. Before October 2011, shared drains were privately owned, and all the properties using them were jointly responsible for maintenance. Since 1 October 2011, most shared drains in England and Wales have been transferred to the water and sewerage companies under the Private Sewers Transfer Regulations 2011. This means the water company is now responsible for their upkeep, which is good news for sellers — you can confirm to the buyer that the shared drain is publicly maintained.

Public sewers

Public sewers are maintained by the water and sewerage company. They are typically larger pipes that run under roads, footpaths, and sometimes through private land, collecting waste water from multiple properties and carrying it to sewage treatment works. If a public sewer runs through or near your property, the water company has a legal right of access to inspect, maintain, and repair it. This right of access can affect what you are allowed to build on your land.

Build-over agreements

If you or a previous owner has built an extension, conservatory, or other structure over or close to a public sewer, the water company should have been consulted. A build-over agreement is a formal arrangement that confirms the water company is satisfied the building work will not damage the sewer or obstruct access. If the drainage search shows a public sewer running under a building on your property and there is no build-over agreement on record, the buyer's solicitor will raise this as an enquiry. You may need to apply retrospectively for approval or obtain indemnity insurance.

Section 104 and Section 106 agreements explained

Two types of agreement that commonly appear on drainage search results are Section 104 and Section 106 of the Water Industry Act 1991. These are particularly relevant for newer properties and recently built developments.

Section 104 agreements

A Section 104 agreement is made between a developer and the water and sewerage company. It covers the adoption of newly built sewers on a development site. When a housing estate is built, the developer constructs the drainage infrastructure. The Section 104 agreement sets out the standards the sewers must meet before the water company will adopt them and take over responsibility for their maintenance.

If the drainage search shows a Section 104 agreement that is still in progress (not yet completed), it means the sewers serving the property have not yet been adopted. This is common on newer developments. The buyer's solicitor will want to know when adoption is expected to complete, because until it does, the developer (or, in some cases, the property owners collectively) may be responsible for maintenance costs.

Section 106 agreements

A Section 106 agreement under the Water Industry Act 1991 gives a property owner the right to connect their private drain to an existing public sewer. The water company cannot unreasonably refuse a connection, but it can set conditions — for example, specifying the method of connection and requiring that the work is carried out to an approved standard.

It is important not to confuse this with a Section 106 planning agreement under the Town and Country Planning Act 1990, which relates to developer obligations such as affordable housing contributions. The drainage search specifically relates to the Water Industry Act version.

Properties not connected to mains drainage

Not every property in England and Wales is connected to the public sewer network. Around 5% of properties use private drainage systems, including septic tanks, cesspits (also called cesspools), sewage treatment plants, and drainage fields. If your property relies on one of these systems, the drainage search will confirm this — and it is an area where buyers and their solicitors will ask detailed questions.

Since 1 January 2020, the Environment Agency's general binding rules have applied to septic tanks and sewage treatment plants in England. These rules require that:

• Septic tanks must not discharge directly into a watercourse (river, stream, or ditch). If yours does, it must be replaced or upgraded to a full sewage treatment plant.
• Sewage treatment plants must meet minimum standards for effluent quality if they discharge to a watercourse.
• All private drainage systems must be properly maintained and regularly desludged.

As a seller, if your property has a private drainage system you should gather your maintenance records, any Environment Agency permits or exemption certificates, and evidence that the system complies with the general binding rules. Being prepared with this information prevents delays when the buyer's solicitor raises enquiries. For more on how to handle issues flagged during searches, see our guide on what to do if searches reveal problems.

Common issues the drainage search can flag

Most drainage searches come back without any significant problems. However, there are several issues that can arise and prompt the buyer's solicitor to raise additional enquiries.

• Public sewer within the property boundary — This is one of the most common findings. It does not prevent the sale, but the buyer will want to know whether any structures have been built over or near the sewer, and whether a build-over agreement is in place.
• No record of mains connection — If the water company has no record of the property being connected to the public sewer, this could indicate a private drainage system or simply an administrative gap. Further investigation will be needed to clarify.
• Incomplete Section 104 agreement — On newer developments, an ongoing Section 104 adoption process means the sewers have not yet been taken over by the water company. The buyer may want confirmation of the expected adoption date.
• Property near a sewage treatment works — If the search shows a sewage treatment facility nearby, the buyer may have concerns about odour or future development plans. This does not usually prevent a sale but may require additional information.
• Surface water not connected to the public sewer — If rainwater from the property does not drain to the public network, the property may use soakaways or other private arrangements that require maintenance.
• Combined sewer system — In older areas, foul water and surface water may drain into the same combined sewer. This is not a defect, but combined systems can be more susceptible to overloading during heavy rain, and it may be noted in the report.

How the drainage search fits into the conveyancing timeline

The drainage and water search is one of several standard searches ordered by the buyer's solicitor early in theconveyancing process. It typically sits alongside the local authority search, the environmental search, and any additional searches specific to the property's location. For a full overview of the standard pack, see our guide on property searches explained.

In terms of timing, the drainage search is one of the faster searches to return. Most water companies deliver results within 1 to 5 working days, compared with the 2 to 6 weeks that a local authority search can take. This means the drainage search itself rarely causes delays — but the enquiries it generates can.

If the drainage search flags something unexpected, such as a public sewer under an extension or no record of a mains connection, the buyer's solicitor will raise enquiries with your solicitor. If you are unable to answer these questions promptly, the back-and-forth can add days or weeks to the process. This is why preparation matters. Knowing your drainage arrangements before you list helps you respond quickly and keeps the overall conveyancing costs under control.

What sellers can do to prepare

You do not need to wait for the buyer's solicitor to order the drainage search to understand what it will show. There are several practical steps you can take before you list your property.

1. Check your water company's sewer map — Most water companies in England and Wales provide a free online sewer map that shows the location of public sewers near your property. This is the same data that forms part of the CON29DW results.
2. Know your drainage type — Are you connected to mains drainage, or do you use a septic tank, cesspit, or private treatment plant? If the latter, gather your maintenance records and any permits.
3. Check for build-over agreements — If any part of your property has been built over or near a public sewer, check whether a build-over agreement was obtained. Your local water company can confirm this.
4. Review your title deeds — Your deeds may contain easements granting the water company (or neighbouring properties) rights of access for drainage purposes. Your solicitor can help you understand these.
5. Consider ordering the search upfront — Sellers can order a drainage search through their conveyancer or through a service like Pine. Having the results ready for the buyer's solicitor can shorten the process. Many buyer solicitors will accept an existing drainage search if it was produced by the official water company and is recent.

Being proactive about drainage is one of the simplest ways to reduce delays. Unlike issues such as planning history or environmental contamination, drainage questions are usually straightforward to answer once you know the facts.

The 2011 private sewer transfer: what it means for sellers

Before 1 October 2011, many shared drains and lateral drains in England and Wales were privately owned. This meant that the property owners whose homes connected to these drains were collectively responsible for their repair and maintenance. In practice, this caused confusion and disputes, especially when an expensive repair was needed and owners could not agree on who should pay.

The Private Sewers Transfer Regulations 2011 transferred the ownership of most of these shared and lateral drains to the water and sewerage companies. Since then, the water company has been responsible for maintaining them. This was a significant change that benefits sellers, because it removes a common source of buyer concern. When the drainage search shows that shared drains serving the property are now publicly maintained, it provides reassurance that the buyer will not inherit unexpected repair costs.

There are exceptions. Some private sewers and drains were not transferred — for example, those serving a single property (a private drain rather than a shared one) and some drains on commercial or industrial premises. If the drainage search indicates that a drain serving your property was not transferred, the buyer's solicitor will want more detail about the maintenance arrangements.

Sources and further reading

• Law Society — CON29DW Drainage and Water Enquiries form and guidance: lawsociety.org.uk
• Water Industry Act 1991 — Sections 104 and 106, covering sewer adoption and connection rights: legislation.gov.uk
• Private Sewers Transfer Regulations 2011 — Statutory instrument transferring shared drains to water companies: legislation.gov.uk
• Environment Agency — General binding rules for small sewage discharges in England: gov.uk/guidance/general-binding-rules-small-sewage-discharge-to-the-ground
• Ofwat — Water and sewerage company regulation and consumer guidance: ofwat.gov.uk
• Thames Water — Example sewer map and build-over agreement guidance: thameswater.co.uk
• Gov.uk — Guidance on private water supplies and regulations: gov.uk/government/collections/private-water-supplies
• Council of Property Search Organisations (CoPSO) — Standards for regulated search providers: copso.org.uk

Frequently asked questions